Because the price of optical fiber switches is still very high,
fiber is mainly used for connection between core switches and
backbone switches, or for cascading between backbone switches. It
is important to note that fiber ports of switch (fiber media
converter) can not be stacked, and can only be used for cascading.

When a backbone switch is connected to a core switch, a crossover
fiber optic jumper must also be used between the transmitting port
and receiving port.

The fiber optic jumper is divided into single mode and multimode.
Fiber port of switch (fiber media converter) and optical fiber
patch cord must be consistent with the optical fiber type of
integrated wiring, that is to say, if the integrated cabling used
multimode fiber, the fiber port of switch must implement the
1000Base-SX standard, also must use multimode fiber optic jumper;
if the integrated cabling used single-mode fiber, fiber interface
of switch must be the implementation of 1000Base-LX/LH standard,
also must use single-mode optical fiber patch cord.

It is important to note that there are two types of multimode
fiber, that is, 62.5/125μm and 50/125μm. Although the fiber ports
of switches are exactly the same, and both perform the 1000Base-SX
standard, it is still not enough, the core diameter of the fiber
optic jumper must be exactly the same as the core diameter of the
optical fiber cable.

Otherwise, it will result in connectivity failure. In addition, the
types of optical ports of interconnected switches must be exactly
the same, or they are all multimode optical fiber ports or single
mode optical fiber ports. If one end is multimode fiber port, while
the other end is single mode fiber port, they can not be connected.